1. Field of the Invention
This invention relates to a power device and, more particularly, to a power device used for saving power in a standby mode.
2. Description of the Related Art
At present, electrical equipment in life increases rapidly. The electrical equipment, such as audio/video products and office equipment, has still a large power consumption problem during a standby period, which consumes electrical power and money and also has a bad effect on environment. For the above reason, corresponding regulations are used to strictly limit power consumption of most of the present products during the standby period. The standby mode is a state that the most function of a product is turned off and the basic function which the product needs in the standby mode is turned on and the product is waiting for rebooting by a user. For example, when a display is in the standby mode, a user can use a remote controller to reboot the display to normally operate.
A power supply is mainly used to provide power with a stable and suitable voltage for a single or a plurality of electrical devices, and it is one of necessary and important function elements. Generally, the power supply can convert inputted AC commercial power into DC power needed by an electrical device. In FIG. 1, a conventional power device 1 usually includes an AC/DC power converter 11 and a DC/DC power converter 12 for power conversion. The AC/DC power converter 11 is used to convert an AC voltage (commercial power) to a DC voltage, and then the DC/DC power converter 12 converts the DC voltage to different kinds of DC low voltages needed by loads 6 in an electrical device.
In the conventional power device 1, there are converting losses of the AC/DC power converter 11 and the DC/DC power converter 12, since the AC/DC power converter 11 provides constant voltage no matter whether the electrical device is in a normal operating state or a standby mode, so that it still need the DC/DC power converter 12 that causes the additional voltage converting lose in the standby mode. Thus the performance of the power device 1 is affected and the power saving effect is also affected.